General support of facilities is sought for a research program directed at the relation between structure and function of excitable tissues at the cellular level. Emphasis is given to sensory physiology, especially at the receptor level. The program involves a group of established investigators who have collaborated in some aspects of this problem. The studies proposed involve receptor mechanisms of carotid body chemoreceptors, mammalian sensory pathways, invertebrate neurons of aplysia ganglion cells, barnacle photoreceptors, mammalian retina, ion mechanisms in excitable tissues and structural development of the nervous system with special reference to sensory structures. The support requested is for salaries of some faculty members, key technical personnel and isotope counting equipment. This item is necessary in the study of possible transmitters or generator substances present in some receptors. Electron microscope and histological facilities are already available. Also, the department has a computer for quantitative analysis of nerve discharges which change in frequency during receptor stimulation. Voltage clamp techniques will be used in receptors where anatomical conditions are favorable. Ion exchange electrodes will be used to study processes of excitation and inhibition in excitable tissues. It is expected that the gathering of information in invertebrate tissues may lead to an understanding of processes in mammalian receptors. Afferent and efferent pathways modulating sensory activity will be studied.